Latent heat store

ABSTRACT

A latent heat store is provided having a plurality of heat exchanger units ( 2 ) arranged alongside one another with each being at least one phase change store in which a heat exchanger fluid with the storage medium flows at least between adjacent heat exchanger units ( 2 ). Latent heat store improved heat management is achieved by at least one common intake ( 10 ) for supplying the heat exchanger fluid to the heat exchanger units ( 2 ) and for dividing this fluid into a plurality of separate partial flow sections and also at least one common drain ( 11 ) for discharging the heat exchanger fluid from the heat exchanger units ( 2 ) and for bringing all partial flow sections back together such that the heat exchanger units ( 2 ) of the stack ( 13 ) collectively exposed to the flow are connected in parallel to one another wherein a variety of flow patterns are provided.

The invention relates to a latent heat store comprising a plurality ofheat exchanger units which are arranged alongside one another and eachcomprise at least one phase change store according to the preamble ofClaim 1.

PRIOR ART

At present, the use of so-called latent heat stores is increasinglybeing discussed and promoted. Latent heat stores are used for thetemporary intermediate storage of heat, with a phase change of thewidest variety of substances in the event of a change in temperaturebeing utilized. In recent years, a preferred field for the applicationof such latent heat stores has primarily also become vehicles withinternal combustion engines or fuel cells with or without reformation.In this case, the waste heat which arises during operation is preferablyintermediately stored in an appropriate latent heat store, in order toprovide heat energy for the start-up phase, primarily after a pause inoperation where the engine is switched off, for preheating or heating upthe widest variety of components, such as catalytic converters, enginecomponents or the like.

In coming years, this will have to be taken into considerationincreasingly owing to ever stricter emission regulations. In the case ofinternal combustion engines, the start-up phase specifically forms arelatively large number of undesired or harmful exhaust gas components,which form because vehicle components are not yet at operatingtemperature. Of considerable importance in this context are not only thecatalytic converters, which to some extent are used diversely, but alsocomponents of the combustion chambers of the engine and moving parts ofthe engine.

A good heat exchange between the heat store masses, or the phase changematerial, and the heat exchanger fluid, in particular the heat exchangerliquid, is decisive for discharging and charging the heat stores.

By way of example, DE 41 33 360 C2 and DE 38 21 358 A1 have alreadydisclosed latent heat stores with phase change material, wherein theheat exchanger fluid does not flow rectilinearly between the entranceand the exit of the latent heat store on the shortest path, but insteadby detours, and therefore by an extended flow path through the store. Asa result, an improved uptake and/or release of the heat between phasechange store material and heat exchanger fluid should be achieved.

In addition, DE 90 05 049 has already disclosed a cylindrical latentheat store, in which the heat medium is supplied to the individualsegments on one side of the cylinder and then the heat medium flowsthrough the heat segments from this point transversely to the oppositeside, and the heat medium is collectively discharged in an appropriatemanner in a lateral collection channel.

In addition, DE 4 322 813 has already described the use of vacuuminsulations and of getter elements, and DE 10 2004 023 347 A1 hasalready described the use of thin-layer electric heaters between twoflat sides of two adjacent heat segments.

However, it has been found that such latent heat stores cannot realizeoptimum charging and therefore also discharging of heat, since regionsof differing warmth or fewer warm regions arise. Accordingly, thestorage size of the latent heat store or the power density, i.e. theamount of power per unit volume, of such latent heat stores is also notoptimal.

OBJECT AND ADVANTAGES OF THE INVENTION

In this respect, it is an object of the invention to propose a latentheat store of the type mentioned in the introduction, with whichimproved heat management, in particular in relation to the charging ofheat and the discharging of heat, is realized, and/or with which animproved usability for mobile applications is realized.

Proceeding from a latent heat store of the type mentioned in theintroduction, this object is achieved by the characterizing features ofclaims 1, 2, 4 or 7. Advantageous embodiments and developments of theinventions are possible by virtue of the measures mentioned in thedependent claims.

Accordingly, a latent heat store according to the invention isdistinguished, by way of example, by the fact that at least one commonintake for supplying the heat exchanger fluid to the heat exchangerunits and for dividing said fluid into a plurality of separate partialflow sections and also at least one common drain for discharging theheat exchanger fluid from the heat exchanger units and for bringing allpartial flow sections together are provided, such that the heatexchanger units arranged between the intake and the drain form a stackcollectively exposed to the flow, and such that the heat exchanger unitsof the stack collectively exposed to the flow are connected in parallelto one another, wherein the inflow point of the heat exchanger unit isarranged in the central region of the heat exchanger unit and theoutflow point of the heat exchanger unit is arranged in the radiallyoutwardly arranged casing region of the heat exchanger unit, or whereinthe inflow point of the heat exchanger unit is arranged in the radiallyoutwardly arranged casing region of the heat exchanger unit and theoutflow point of the heat exchanger unit is arranged in the centralregion of the heat exchanger unit, such that the heat exchanger fluidflows in the radial direction along the heat exchanger unitssubstantially over the entire cross section thereof, wherein the lengthof all partial flow sections of the heat exchanger fluid from the intaketo the drain is substantially of equal length.

According to the invention, the sums of all lengths of the individualflow paths between the entrance and the exit of the latent heat storeare approximately the same in the case of parallel flow through thestack. In contrast to the latent heat store disclosed in DE 90 05 049,this applies according to the invention substantially to the entirecross section of each heat exchanger unit, since the fluid flowsradially from the inside outward or radially from the outside inward.Accordingly, according to the invention the same pressure losses arerealized in the entire inner region of the housing or along the surfacesof all heat exchanger units and therefore along all partial flowsections.

By contrast, according to DE 90 05 049, the fluid flows through theregions outside the direct, rectilinear connection line of the twoinflow and outflow points each arranged on the outside at the edge ofthe cylinder and on opposing sides to a significantly smaller degreecompared to the direct intermediate region along the straight, centralconnection line.

According to the invention, provision is preferably made of a centralinflow or alternatively a central outflow of the heat medium in thecenter of the preferably substantially circular housing and/or the heatexchanger units or segments. In each heat exchanger unit, the heat fluidtherefore preferably flows from the centrally or axially arranged inflowpoint from inside in the radial direction and primarily advantageouslyover the full extent or over the entire cross section or over the entirecircumference of the heat exchanger units uniformly outward to thepreferably substantially annular outflow point or to the lateral surfaceof the housing or of the heat store, where it is collected andcollectively discharged. Alternatively, the heat fluid is guided fromoutside via the substantially annular inflow point or from the lateralsurface of the housing/heat store in the radial direction andsubstantially over the full extent over the entire cross section orcircular surface inward to the central or axially arranged outflowpoint.

This radially oriented flow of the fluid leads to a considerably betteror to an optimum heat distribution with all-over uniformity over thecross section of the heat exchanger units. By contrast, in the prior artthere are edge regions through which the fluid flows to a lesser extenton both sides of the connection line formed centrally and rectilinearlythrough the heat exchanger plates. In these edge regions, in the priorart the heat fluid on the one hand has to cover a path which issignificantly greater, specifically by as much as the factor Pi/2 (i.e.about 1.7), than a rectilinear connection line directly through thecenter or a direct connection line which corresponds exactly to thediameter. On the other hand, in the prior art dead regions are formedfor the heat fluid laterally alongside said connection line, in whichdead regions said fluid has regions of return flow/vortices and/or onlya very low flow or possibly even no flow at all. Therefore, existinglatent heat stores cannot realize optimum charging and therefore alsodischarging of heat, since regions of differing warmth or fewer warmregions arise. Accordingly, the storage size of the latent heat store orthe power density, i.e. the amount of power per unit volume, of existinglatent heat stores is also considerably poorer than in the case of theinvention.

By way of example, the heat exchanger units according to the inventionhave a short intake flow path in the region of the intake, but acorrespondingly long drain flow path to the drain of the latent heatstore. In the case of heat exchanger units in the region of the drain,the situation is accordingly the opposite, i.e. a long intake flow pathbut a correspondingly short drain flow path. According to the invention,however, the sum of the intake flow path to the heat exchanger unit andthe path along the heat exchanger unit plus the drain flow path of saidheat exchanger unit is virtually the same for all heat exchanger unitsof the stack and over the entire circumference of the heat exchangerunits.

Alternatively or in combination therewith, the flow resistances of allpartial flow sections of the heat exchanger fluid from the intake to thedrain are substantially of the same magnitude. By way of example, thecross-sectional ratios and the length ratios of the individual partialflow sections are matched to one another in such a manner, e.g. by meansof throttle and/or regulating elements, that the approximately identicalflow resistances are established.

Given substantially identical cross-sectional ratios of the individualpartial flow sections, it is preferable that flow resistances ofapproximately the same magnitude are realized by the length of allpartial flow sections of the heat exchanger fluid from the intake to thedrain being substantially of equal length.

Accordingly, it is an advantage of the invention that all heat exchangerunits of the stack are exposed to approximately the same pressure losseson account of the features according to the invention, and thusapproximately identical volumetric flow rates are established for theindividual heat exchanger units. This in turn has the effect thatapproximately identical heat flows are supplied to and discharged fromthe heat exchanger units, which in turn leads to the same or morehomogeneous charging and discharging of the phase change stores of theheat exchanger units for the entire stack, such that a virtually optimumheat distribution is achieved throughout the latent heat store.Accordingly, in contrast to the prior art, the latent heat storeaccording to the invention can also make use of its maximum storagecapacity.

For the case of application, this means that the highest or the maximumpossible energy density/power density is achieved for the structuralvolume of the latent heat store used. Consequently, compared to theprior art, given an identical amount of useful heat the requiredstructural volume of the latent heat store is reduced, which is acrucial advantage specifically for applications with very limitedavailable space, e.g. in vehicle applications, etc.

With a latent heat store according to the invention, it is possible toprovide more heat energy, e.g. to exhaust gas catalytic convertersand/or components of the engine, etc., than is achieved with latent heatstores according to the prior art given the same structural volume aftera preceding stoppage phase.

The latent heat stores disclosed in DE 41 33 360 C2 and DE 38 21 358 A1have a serial connection of appropriate heat exchanger units, such thata higher temperature level and therefore greater amounts of heat energyare stored at the intake of the latent heat store than is possible inthe drain region of the latent heat store in the case of cooled heatexchanger fluid. Accordingly, primarily the existing heat exchangerunits cannot store an optimum or high amount of energy in the outflowregion of the latent heat store, which leads to a relatively low energyefficiency for the entire stack or latent heat store.

It is preferable that all heat exchanger units have a substantiallyidentical form. It is thereby possible for a stack to be formed fromidentical heat exchanger units, such that the production of theindividual heat exchanger units is improved on account of the productionof a relatively large number of identical heat exchanger units.

In a particular development of the invention, the housing has asubstantially cylindrical form. In contrast to a cuboidal housing of thelatent heat store, a cylindrical housing has improved stability andpressure properties and also flow properties.

It is also possible for numerous identical heat exchanger units to bestacked advantageously both in a cuboidal and in a cylindrical housingin the longitudinal direction of the housing or along the centralmid-axis. This is a major advantage primarily in the case of virtuallyidentical heat exchanger units, since these housings have no significantchanges in cross section along the stack, primarily if the stacks arecorrespondingly oriented transversely in or perpendicular to thedirection of the central mid-axis or longitudinal axis.

By way of example, this is a central difference in relation to the stackand to the passage of flow through the latent heat store according to DE41 33 360 C2, wherein the stacks are not stacked transversely to themid-axis, but rather in the direction of the mid-axis, such that theyhave to have the widest variety of cross-sectional areas in the case ofthe cylindrical housing disclosed. Accordingly, in this case it is notpossible to produce and stack any identical heat exchanger units, as isadvantageously effected however according to the present invention.

It is preferable that the heat exchanger units are producedsubstantially from high-grade steel, with the provision of a high-gradesteel with relatively good thermal conductivity being advantageous.Accordingly, a high chemical resistance and also an advantageous thermalconductivity function of the heat exchanger units are achieved.

In the case of a latent heat store according to the preamble of Claim 1and/or as an advantageous variant of inventive features mentioned above,the object of the invention can also be achieved in that the heatexchanger units have at least one spacer for fixing a spacing for theheat exchanger fluid to flow through between the heat exchanger units.It is thereby possible for separately producible and/or mountablespacers and/or fixings for producing a spacing between the heatexchanger units to be dispensed with. This leads to a particularlyadvantageous production of the latent heat store according to theinvention. The spacers according to the invention for the heat exchangerunits have the effect that a defined through-flow of the heat exchangerfluid in the intermediate region between two heat exchanger units isensured. This leads to advantageous flow conditions and pressure losseswithin the latent heat store or the stack according to the invention,which in turn ensures advantageous heat management in terms of thecharging and discharging of the latent heat store.

It is preferable that the phase change stores comprise at least thespacers and that the phase change stores are in the form of spacers.This means that the phase change stores are dimensioned in such a waythat they realize a predefined or defined spacing between two heatexchanger units, and at the same time form open flow cross sections forthe heat exchanger fluid between the heat exchanger units. Primarily inthe case of identical heat exchanger units, it is also ensured in thisrespect that identical flow conditions and therefore pressure losses areensured between the individual heat exchanger units, which leads to anadvantageous flow through the entire stack or latent heat store.

In an advantageous embodiment of the invention, the spacers are in theform of a bend of a heat exchanger unit. By way of example, the heatexchanger units can be produced from deformed/reformed metal sheets, inwhich case by way of example two advantageously shaped metal sheets areconnected to one another in such a way that a storage volume for thephase change material is generated. For heat exchanger units which arecorrespondingly produced from sheet material or else heat exchangerunits which are produced from metal in another way, it is possible toprovide advantageous bends, which at the same time are in the form ofspacers according to the invention. This leads to a particularlycost-effective method for producing the individual heat exchanger unitsand therefore the entire latent heat store.

By way of example, the bends may fulfill not only spacing functions, butalso further functions, e.g. centering, i.e. alignment in relation tothe central mid-axis and/or to the housing, and/or also a fixingfunction in terms of twisting, adjustment of the heat exchanger unitsboth in the transverse direction and in the longitudinal directionand/or in the radial direction of the latent heat store according to theinvention. On account of the numerous functions which can be realized byspacers and/or bends, the latent heat store according to the inventionis realized with an advantageous design and such that it can bemanufactured cost-effectively.

Alternatively or in combination therewith, it is also possible forexample for adjacent heat exchanger units to be welded or spot-welded toone another or fixed cohesively to one another and/or spaced apart, inorder inter alia to suppress a relative movement therebetween, such thatas far as possible there is no change concerning the flow paths orpressure losses between the heat exchanger units and/or between heatexchanger units and the housing even in the long term. The heatexchanger units, which preferably consist essentially of sheet metal, orthe phase change stores can therefore have inter alia depressions orrecesses such as grooves, etc., and/or protrusions or elevations or thelike, in order to ensure an advantageous fluid flow and/or spacingand/or fixing/holding between two adjacent heat exchanger units and/orin relation to the housing of the latent heat store.

A latent heat store according to the preamble of Claim 1 and/oraccording to one of the above-mentioned embodiments can advantageouslybe distinguished by the fact that the heat exchanger units have at leastone anti-twist device for preventing radial twisting of heat exchangerunits. It has been found that this is advantageous specifically whenradially symmetrical housing forms or heat exchanger units are used. Inthis case, anti-twist means primarily make advantageous, stable flowconditions possible between the heat exchanger units or in the latentheat store according to the invention. These clearly defined flowconditions in and around the stack or within the latent heat store,which as far as possible are stable even over relatively long periods oftime, in particular throughout the service life of the latent heatstore, are of significant importance, for avoiding disadvantageouseffects concerning the maximum realizable energy density or storagecapacity.

It is preferable that the spacers of the heat exchanger units are in theform of an anti-twist device. A corresponding multiple function reducesthe outlay on design and therefore production.

The housing advantageously has at least one thermal insulation unit as asheathing. It has been found that primarily a vacuum insulation unit isparticularly advantageous, since a distinctly high or advantageousthermal insulation action is achieved with a relatively small insulationvolume. This is particularly advantageous primarily for vehicleapplications, since in this case there is generally relatively littlespace available.

A particularly advantageous embodiment, which achieves the objectaccording to the invention, of a latent heat store according to thepreamble of Claim 1 having a vacuum insulation unit as a thermalinsulation unit and/or according to one of the above-mentioned variantembodiments is distinguished by the fact that the vacuum insulation unitcomprises at least one getter unit with a getter material. Anadvantageous getter material ensures a particularly advantageous vacuumin the vacuum insulation unit. In this respect, the gas molecules enterinto a direct chemical bond with the atoms of the getter material at thesurface of the getter material, or the gas molecules in the vacuum aredetained by sorption. As a result, gases or molecules which remain areappropriately bound in the vacuum, such that the vacuum of the vacuuminsulation unit can be improved or can be retained even over arelatively long time.

As the getter material, use is made for example of barium, aluminum,titanium, zirconium and/or magnesium and/or the alloys thereof. Thegetter material is preferably in the form of disks, pellets, rings orthe like, and a plurality of such getter units are secured together, forexample, by means of a securing element, for example by means of a metalsheet or the like which is to be formed appropriately.

It is preferable that the getter material is arranged on the side lyingopposite an evacuation opening of the housing or of the insulation unit.Since the getter material acts like a pump, the vacuum can thereby begenerated in an advantageous manner, in which case narrow points or thelike which may be present between the two housings or the opposing sidesof the latent heat store are not disadvantageous for the evacuation.

By heating the getter material, the latter can be regenerated orreactivated, such that substantially the original binding capacity orsorption capacity of the getter material is available again. Thisregeneration or reactivation can be effected very frequently.

The getter material is advantageously arranged in the region of theintake of the latent heat store within the vacuum insulation unit. Byway of example, the heat exchanger fluid can thereby be advantageouslyprovided for heating or regenerating the getter material. Thisregeneration of the getter material can be initiated or carried out, forexample, after predefined time intervals and/or if required by means ofadvantageous sensors or the like.

A vacuum which is advantageous also in the long term in the vacuuminsulation unit is of great advantage primarily for ensuring the highthermal insulation action. Accordingly, the amount of heat stored by thephase change material can also be advantageously provided afterrelatively long periods of time for appropriate applications, such asthe heating of vehicle components or the like.

In principle, waste heat from the cooling water and/or from the exhaustsystem and/or from the brake system and/or from other vehicle componentswhich produce waste heat can be used in vehicle applications for heatstorage according to the invention. By way of example, in the case offuel cell vehicles, too, it is possible to use appropriate amounts ofwaste heat from fuel cell components and/or from stationary heatingsystems or similar contributions for filling the latent heat storeaccording to the invention.

For the latent heat store according to the invention, it is generallyadvantageous to provide a heat transfer oil or the like as the heatexchanger fluid, which is pumped through the latent heat store or pumpedalong the heat exchanger units, for example by means of an advantageouspump.

In addition, it is advantageous by way of example to provide as thephase change material a salt or the like which has a phase change atabout 200° C., for example. This phase change material is stored in thephase change store or in appropriate chambers of the heat exchangerunits, which, for example, are evacuated.

The latent heat store advantageously has an inner housing, in which thestack with the heat exchanger units is arranged, and an outer housing,with thermal insulation or a vacuum being provided between the innerhousing and the outer housing.

It is preferable that (if possible all) components of the latent heatstore according to the invention which come into contact with the vacuumare formed from high-grade steel, e.g. 1.4301 or the like. Compared tomany other metals, high-grade steel has, for example, a lower outgassingrate.

It is preferable that the vacuum insulation unit at least in parts has asurface layer or a coating for reducing the emissions into the vacuum.By way of example, a relatively favorable material is provided for thevacuum insulation unit or the housing. Losses resulting from heatradiation can be reduced by up to about 50% for example by anadvantageous low-emission coating or surface layer with an advantageousmaterial, such as preferably copper and/or e.g. silver, aluminum, zinc,etc. In principle, it is advantageous to use low-emission materials forthe vacuum insulation unit.

It is advantageous that (if possible all) components of the latent heatstore according to the invention which come into contact with the vacuumare specially treated or formed. Firstly, the surfaces are formed withparticular purity, in order to ensure as far as possible a lowoutgassing rate and/or also a short evacuation time.

In a particular development of the invention, the surface of the vacuuminsulation unit or of (if possible all) components which come intocontact with the vacuum is at least partially advantageouslyelectropolished and/or blasted with glass beads or the like, forexample. By way of example, an emittance of less than 3% can be achievedby the measures according to the invention.

Secondly, all surfaces which emit heat or come into contact with thevacuum should have the smallest possible emittance, in order to keepradiation losses as small as possible. To this end, such surfaces arepreferably likewise electropolished and/or advantageously coated.

Advantageous, for example flexible, holding and/or fixing devices can beprovided for fixing or arranging the inner housing or the stack withinthe outer housing. By way of example, (metal) strips or the like and/orspiral springs or spring elements can be used for holding both in thelongitudinal and/or in the radial direction. Holding components having arelatively poor thermal conductivity (e.g. <10 W/mK) are particularlyadvantageous, such that thermal conduction between the stack or theinner housing and the outer housing is minimized as far as possible.This also applies in relation to advantageous intake lines and/or drainlines between the outer housing and the inner housing or the stack ofthe latent heat store.

As an alternative to or in combination with strips, springs or the like,the holding and/or fixing device can be in the form of a so-calledsupported vacuum insulation system. A supported vacuum insulation systemadvantageously comprises numerous insulating/supporting elements such asinsulating fibers, e.g. made of glass fibers or the like, wherein thespace in which these are arranged is evacuated and, in particularapplications, may be sealed off by means of a sleeve or cladding layer,e.g. made of foil or the like. The inner housing and the outer housingof the latent heat store according to the invention substantiallyadvantageously form the cladding layer, such that a separate oradditional foil or the like can be dispensed with.

In particular applications, if the vacuum insulation system is in theform of a supported vacuum insulation system, it is advantageouslypossible to dispense with an additional holding and/or fixing devicebetween the two housings. In this case, the insulating/supportingelements can perform the holding and/or fixing function. Ifcorresponding (metallic) holding and/or fixing devices are dispensedwith, it is possible to achieve a particularly advantageous insulationaction.

In principle, it is advantageous to form both the holding and fixingcomponents between the two housings and also the intake and drain linesin such a manner that no disadvantageous stresses occur on account ofthermal expansion. By way of example, the intake and/or the drain lineshave a bent form and/or have advantageous regions in order to be able tocompensate for changes in length of the lines as far as possible withlow stresses.

By virtue of the structure according to the invention and theadvantageous geometry of the heat exchanger units with the phase changestore material, flow advantageously passes through the latent heat storeaccording to the invention, such that essentially no dead regions orregions through which flow passes poorly are generated within the store,as was readily the case to a considerable extent to date in the priorart.

Primarily where the latent heat store according to the invention is usedfor electric vehicles or else hybrid vehicles with an electric drivemotor, it may be particularly advantageous for achieving the object ofthe invention to arrange at least one electric heating element forheating the phase change stores and/or heat exchanger units inparticular within the heat exchanger housing.

Specifically in the case of electrically driven vehicles, there arelarge electric accumulators on board, but little or virtually no wasteheat from the drive motor which can be used for the heat absorption forthe latent heat store according to the invention. This inventionprovides that an electric energy supply or heat storage can be realizedin an advantageous manner, for example the most homogeneous possibleheating and therefore storage of the energy/heat introduced.

By way of example, at least two separate latent heat stores according tothe invention are provided in a vehicle. A first latent heat store,which is supplied or charged with heat energy, e.g. waste heat from thebrake system and/or from the electric drive motor, etc., and a secondlatent heat store, which is supplied or charged with electric energy,e.g. from the electric traction battery/accumulator, a photovoltaic unitarranged on the sleeve or outer skin of the vehicle and/or from avehicle-external or stationary energy supply, e.g. from the “electricsocket” or from an electric “filling station”. The vehicle-externalcharging variant of the invention in particular makes it possible forthe latent heat store according to the invention to be supplied orcharged with energy at the same time or additionally during the electriccharging of the traction battery/accumulator, for example.

It is not only possible for a latent heat store according to theinvention to be supplied or charged with a relatively large amount ofenergy very quickly. Rather, a considerably more advantageous energystorage in the vehicle or on board can be realized as a result in viewof a comparison, relating to a weight and/or volume unit and also to thecosts, with energy storage by means of a traction battery/accumulator.Latent heat stores according to the invention can advantageously providethe stored energy/heat inter alia for the air conditioning or heating ofa passenger cabin or the like and/or for preheating vehicle componentssuch as the battery/storage battery, catalytic converters, etc. Ifappropriate, in this latent heat store according to the invention theheat exchanger fluid is in the form of gas, preferably air. This has theeffect that the stored heat/energy can be taken up directly from thegas/air by the heat exchanger units or the phase change material andconducted directly into the passenger cabin in an advantageous manner bymeans of ventilation ducts or the like, for example. As an alternativeor in combination therewith, it is also possible to provide a primaryand a secondary circuit with similar or else different heat exchangerfluids, i.e. liquid and gas/air.

A fan or the like is advantageously provided for gas/air to flow throughthe latent heat store according to the invention.

It is preferable that the heating element is arranged between twoadjacent heat exchanger units. This achieves a particularly effectiveand efficient transfer of energy from the electric heating element tothe heat exchanger units or to the phase change material.

In principle, the electric heating can be realized in the manner of animmersion heater or the like. In a particular development of theinvention, the heating element is in the form of a heating foil. Thisheating foil is relatively thin and can advantageously be brought intodirect contact with the heat exchanger units and thus be arranged veryclose to the phase change material. This additionally improves the heatabsorption.

Specifically in the embodiment in which heat exchanger units have a flator planar side, the use of a heating foil is particularly advantageous.Thus, said heating foil can be arranged or inserted between two planarsides/surfaces of the adjacent heat exchanger units. This is of majoradvantage when numerous heat exchanger units are used or stacked,particularly during production and also in relation to the utilizationof space within the latent heat store according to the invention andalso in relation to the most homogeneous possible heating and thereforestorage of the energy/heat introduced.

In general, it is advantageous specifically also in the case ofelectrically driven vehicles to convert the brake energy into electricenergy using an electric generator, i.e. to recuperate it, and to usethis for heating the latent heat store according to the invention and/orfor charging the traction battery/accumulator.

EXEMPLARY EMBODIMENT

An exemplary embodiment of the invention is shown in the drawing and isexplained in more detail hereinbelow with reference to the figures.

In detail:

FIG. 1 shows a schematic cross section in the longitudinal directionthrough a latent heat store according to the invention,

FIG. 2 shows a schematic cross section in the longitudinal directionthrough an inner part of the latent heat store according to theinvention as shown in FIG. 1, with a heat exchanger stack and innerhousing,

FIG. 3 shows a schematic plan view perpendicular to the longitudinaldirection onto the inner part of the latent heat store according to theinvention as shown in FIG. 1,

FIG. 4 shows a schematic, perspective view of a first heat exchangerunit of the stack shown in FIG. 2,

FIG. 5 shows a schematic plan view of a second, alternative heatexchanger unit for the stack shown in FIG. 2,

FIG. 6 shows a schematic, enlarged sectional side view of two stackedheat exchanger units according to FIG. 2, and

FIG. 7 shows a schematic, perspective view of a getter pellet unit.

FIG. 1 schematically shows a latent heat store 1, i.e. a so-called PCM(Phase Change Material) store 1, according to the invention. Merely forreasons of clarity, heat exchanger units, i.e. so-called sheets 2, inthe interior of the latent heat store 1 are not shown in FIG. 1, but areshown in part in an enlarged view in FIGS. 2, 4, 5. The latent heatstore 1 comprises, as the outer sleeve, an outer housing 3 with acylindrical casing 4 and a base element 5. In addition, a vacuumconnection 7 is visible on the outside, this being used for generating avacuum 9 between the outer housing 3 and an inner housing 8 and thenbeing closed, in particular crimped. The inner housing additionally hasa cover 27 and a base 19.

Furthermore, both an intake 10 and a drain 11 for a heat exchangerfluid, such as a liquid or a gas, in particular a heat transfer oil, airor the like, are provided on the outside on the side of the outer orinner cover 6, 27. These are preferably used for the input and/or theoutput of the heat energy, which is intermediately stored in the latentheat store 1, in particular by means of the PCM material stored orincorporated in chambers 14 of the sheets 2. The chambers 14 or pocketsare preferably evacuated and/or permanently closed.

Numerous sheets 2 are stacked as a stack 13 or arranged alongside oneanother in the longitudinal direction or along the mid-axis 12 in theinterior of the inner housing 8. As will become clear primarily in FIGS.4 and 5, each sheet 2 comprises a plurality of chambers 14, which arearranged annularly or concentrically around the mid-axis, for example.The sheets 2 are preferably produced from sheet metal, provision beingmade for example of a planar metal sheet and a metal sheet which hasnumerous protrusions intended for the formation of the chambers 14 andwhich is cohesively bonded, in particular (laser) welded, to the planarmetal sheet in an advantageous manner. If appropriate, in each case twosheets 2 are connected to one another, in particular (spot and/or laser)welded to one another, at the respective planar sides (cf. point 15 inFIG. 5), such that the handling is improved during the production and/ormaintenance/repair of the stack 13. In this respect, radial adjustmentof these two sheets 2 in relation to one another is also prevented, suchthat inter alia no change in the flow conditions of the heat exchangerfluid can arise during operation.

An alternative anti-twist means for two sheets 2 which lie against oneanother with the planar side is realized with the variant according toFIG. 4. In this respect, the individual sheets 2 have a plurality oflugs or wings 16 which are arranged on the outside or circumference andare partially bent in the direction of the mid-axis 12 (not shown), suchthat they interlock with corresponding wings 16 of an adjacent sheet 2and/or pair of sheets and thus effectively prevent relative twisting inthe radial direction.

In addition, further (partially bent) wings 31 or lugs 31 are providedin the central region of the sheets 2 and radially align or center thesheets 2 and generate one or more open flow cross-sectional openingswith respect to the pipe 18.

In addition, the chambers 14 have advantageous surface structures orso-called combs 17, which are in the form of spacers in relation to thespacing between two adjacent sheets 2 preferably in the direction of thelongitudinal axis or mid-axis 12 (cf. FIG. 6). These combs 17 are showninter alia in FIGS. 4 to 6, in which case one or by way of example moregrooves oriented in the radial direction are in the form of combs 17.The sheets 2 have an inflow point 34 in the region of a centric or axialmid-point or in the region of the longitudinal axis 12. An outflow point35 is provided according to the invention directed circumferentially oroutward with respect to the casing or housing 8. In this exemplaryembodiment, the outflow point 35 has a substantially annular form or isin the form of a ring.

Alternatively, said ring or the outer circumference could also be in theform of an inflow point and the center hole or the center could be inthe form of an outflow point according to the invention, wherein anadvantageous radially oriented flow of the heat exchanger fluid islikewise realized over substantially the full extent of the crosssection or over the circular surface of the sheets 2.

The preferably radially oriented combs 17 produce a gap 33 through whichthe heat exchanger fluid flows preferably in the radial directionapproximately perpendicular to the longitudinal direction 12, such thatthe fluid can flow around the chambers 14 virtually over the entire areathereof and in the radial direction. This makes advantageous heatexchange possible between the fluid and the PCM material.

For vehicle applications, it has been found that a PCM material having aphase change approximately in the region of about 200° C. isparticularly advantageous. To this end, use should also be made of asuitable heat exchanger fluid, in particular a heat transfer oil, whichis suitable for this temperature range.

The fluid is supplied to the sheets 2 or the inflow points 34 thereof orto the stack 13 using a pipe 18, which is arranged approximatelycentrally in the longitudinal direction 12 and is spaced apart from abase 19 of the inner housing 8. An open end 20 of the pipe 18advantageously has a so-called crown design, in order inter alia tocompensate for possible assembly/component tolerances, i.e. to prevent asufficient opening cross section for the fluid flowing out from beingdisadvantageously undershot even in the case of a slightly variablespacing between the end and the base 19 (even in the case of contact).

To compensate for or to reduce stresses which are caused by a change inlength and can arise as a result of different temperatures of the sheets2 or of the fluid, and to fix/hold the sheets 2 or the stack 13, aninner spring element 21 is provided. However, this spring 21 not onlycompensates for thermally induced changes in length of the stack 13, butalso presses the sheets 2 against one another, such that for example thetransfer of heat to contact surfaces, in particular the planar side (cf.above), is also improved. In addition, this prevents the sheets 2 fromlying only loosely against one another and prevents the gaps 33 whichare fixed between the chambers 14 with the aid of the combs 17 or thelike from unintentionally being increased or widened, which could leadto a disadvantageous or undesired change in the flow conditions of theheat exchanger fluid in the inner housing 8. By way of example, the gaps33 between the chambers 14 have a thickness of about 0.5 mm or a fewmillimeters.

Furthermore, to compensate for the thermally induced change in length, asleeve 28 is arranged on the pipe 18, in order inter alia to prevent anupper pressure plate 29 from becoming caught during adjustment and alsoa disadvantageous flow of the heat exchanger fluid along the pipe 18.The pressure plate 29 advantageously distributes the locally introducedspring force of the spring 21 over the entire radius. So that this iseffected as homogeneously as possible, the pressure plate 29 has aslightly conical profile of about 1° toward the center.

In the region between the inner and outer housings 3, 8, the intake 10and the drain 11 have regions for compensating for thermally inducedchanges in length, e.g. in particular metal bellows 30 or the likeprovided in the bend region.

As already mentioned, the inner container/housing 8 is thermallyinsulated with respect to the outer housing 3 by means of a vacuum 9. Toimprove the vacuum 9, a getter material or getter pellets 25 is or areadvantageously arranged on the inner and/or outer housing 3, 8 and/or onfixing/holding devices such as clamping or spring elements 22, 23, 24and/or on the intakes/drains 10, 11. The getter pellets 25 arepreferably arranged on the outer housing 3, in particular on the base 5,and/or on the intake 10 by means of a holder 26. As a result, when thegetter material is charged the getter material or the getter pellets 25can advantageously be regenerated by heating. In this case, theregeneration heat can be conveyed from outside through the wall orthrough the base 5 to the getter pellets 25 by means of a separate heatsource and/or by means of the heat exchanger fluid.

In principle, the holder 26 should conceal the surface of the getterpellets 25 as little as possible, in order to make the advantageousaccumulation of remaining atoms or molecules of the vacuum 9 possible.

The fixing/holding devices such as clamping or spring elements 22, 23,24 hold and fix the inner container or housing 8 at a spacing from theouter housing 3. These elements should as far as possible be formed insuch a manner that relatively poor thermal conduction by the latter isobtained. For this purpose, these can be produced inter alia in arelatively long and thin form or with a small cross section and alsofrom appropriate material. By way of example, a high-grade steel havingrelatively poor thermal conduction properties can be used for thispurpose.

FIG. 3 shows the preferred installation position. The holders or springs23 and 24 have webs 32, which are oriented in the direction of thegreatest expected acceleration, in this case primarily in the verticaldirection. In addition, it becomes clear in FIG. 3 that the drain 11runs in the vertical direction, in order to minimize convection lossesby the heat exchanger liquid.

According to the invention, an advantageous throughflow is realized,this being explained in more detail hereinbelow. The fluid flows throughthe intake 10 to the pipe 18 and enters into the inner space of thelatent heat store 1 at the open end 20. Here, an annular contact surfaceof the lowermost sheet 2 together with the base 19 preventsunintentional “underwashing” of the lowermost sheet 2. On account ofthis, the fluid flows inter alia to the first/lowermost inflow point 34between the lowermost and the second lowest sheet 2 in the radialdirection past the chambers 14 thereof or the lowermost/first gap 33 tothe outflow point 35 or to the circumference or outer edge of the sheets2. Then, the fluid flows along further outflow points 35 of the othersheets 2 and along the casing of the housing 8 to the cover 27 andthrough the drain 11 out of the latent heat store 1.

A second flow path branches off at the open end 20 in such a manner thatthis partial flow flows back/up along the pipe 18 and then, at the nextinflow point(s) 34, through the next or second gap 33 between twoadjacent sheets 2 or chambers 14 and in the radial direction to theouter circumference or to the next outflow point(s) 35 of the nextsheets 2 and then in turn along further outflow points 35 of the othersheets 2 and along the casing of the housing 8 to the cover 27 or drain11. The same applies to the third, fourth, fifth, etc. gap 33 of thestack 13.

It is essential in relation to the flow according to the invention ofthe individual partial flows that the sum or length of the individualpartial flows connected/realized in parallel from the open end 20 to thedrain 11 is approximately the same, even in relation to thecomprehensive radial flow of the fluid from the center or the inflowpoint 34 to the outflow point 35 or to the circumference of the sheets2. This brings about identical pressure conditions or hydraulic orpneumatic resistances and therefore identical flow velocities orvolumetric flow rates along the sheet 2 or the chambers 14 and also inthe inner housing 8. This prevents dead spaces, through which flowpasses only poorly or to a small extent. The system additionallyregulates itself in an advantageous manner.

The text which follows mentions various components of the latent heatstore 1 if appropriate with further properties or advantages.

The slide bushing or sleeve 28 is intended to prevent tilting of thepressure plate upon thermal expansion and “slide” on the oil guidingpipe 18. For this reason, the bushing material is preferably brass.Brass and high-grade steel have good sliding properties. Furthermore,the tolerances between the slide bushing 28 and the oil guiding pipe 18are selected to be as small as possible, in order to have the smallestpossible gap between the components, which permits no or only a verysmall bypass leakage. Likewise, the height or the gap length should bemaximized for the installation, in order for it to be possible toprovide the narrowest and longest possible gap.

In the installed state, the spring 21 inside should apply a definedcontact pressure of the pressure plate 29 to the PCM stack 13. In thecase of a vehicle, this contact pressure should be at least as great asthe maximum lateral acceleration which occurs. In one application, aspring force of about 220-250 N is selected. This should be ensured forall thermal states. This means that, for example at about −40° C., thePCM stack height is reduced by about 5 mm as compared with about 20° C.At an operating temperature of about 250° C., the height increases byabout 5 mm, for example, as compared with 20° C. The material of thespring 21 should be suitable for temperatures of >about 350° C., sincethe spring preload has to be retained after the heat-treatment processfor evacuation.

At the lower side or the open end 20, the oil guiding pipe 18 has a“crown design”. The design is chosen such that the “tips” of the crowncannot act as a cutting edge in the case of direct contact with the base19. The crown is intended to prevent blockage of the oil flow, shouldthe pipe 18 be incorrectly installed until contact or should the pipe 18be present on the base 19 on account of thermal distortion. Furthermore,it serves for additional centering of the PCM stack 13 and conveys thefluid or heat transfer oil to the base 19 of the store 1.

The pressure plate 29 serves as an “end cover” of the PCM stack 13. Thisend cover 29, together with the slide bushing 28, is intended to preventa bypass leakage, in that the plate 29 conducts the oil flow in any casethrough the uppermost level of the PCM sheet. Furthermore, the pressureplate 29 has the task of distributing the spring force, which isintroduced locally at the spring seat, as homogeneously as possible overthe entire radius. Therefore, the pressure plate 29 tapers conicallytoward the center at about 1°. If appropriate, the material thickness ofthe pressure plate 29 may be reduced by introducing beads and/or ribsetc. for stiffening and distributing forces. Lugs of the plate 29 whichare bent upward additionally serve as centering for the spring 21.

Casing of the housing 8: the special feature here is that the outersurface of the inner casing should be electropolished, for example. Thisreduces impurities, which would be very harmful during evacuation, andreduces the emittance of the surface and improves the outgassing rate. Areduction in the emittance leads to a reduction in the radiation losses.In addition, the outer surface should be completely free of dirt andgrease.

The PCM sheets 2 are preferably welded together from two high-gradesteel sheet halves. One side of the metal sheet has deep-drawn pocketsor chambers 14 into which the liquid PCM is filled. A metal sheet whichlikewise has deep-drawn pockets or chambers 14 or preferably finally aflat, punched metal sheet is welded thereto.

An electrically heatable heating foil or the like (not shown inter aliain FIG. 2 or 6 merely for reasons of clarity) can advantageously bearranged between two flat, adjacent sides of two PCM sheets 2 (e.g.above and/or below the two PCM sheets 2 in FIG. 6). In a particulardevelopment of the invention, the electrical contact is made between theelectric heating elements/foils arranged between two PCM sheets 2 bystacking the PCM sheets 2 one on top of another. In this case, theelectrical connection of PCM sheets 2 to PCM sheets 2 can advantageouslybe “looped through” or passed on. The latent heat store according to theinvention preferably has a common electrical connection on the outsideor on the outer housing 3, e.g. two electric conductors (conductorends), with which the heating element/foil or the numerous heatingelements/foils within the housing 8 or between the PCM sheets 2 aresupplied with electric energy.

In order for it to be possible to set the oil gap in each level,so-called “spacer combs” 17 are integrally formed in each pocket 14. Theindividual pockets 14 are welded in a holding-down device, for exampleby means of a laser. In order for it to be possible to ensure aredundancy, each pocket 14 is preferably provided with twocircumferential weld seams.

In order to fix and align the sheets 2 in the inner casing, wings 16which serve as spacers are fitted on the outside. This spacing is neededsince the oil rises on the casing. The wings 16 also serve as springelements, since instances of radial thermal expansion can occur as aresult of differences in temperature in the sheet 2 itself. This thermalexpansion is compensated for by the resilient wings 16 in anadvantageous manner. In addition, the wings 16 serve as a torsionalbarrier, since the wings 16 engage into one another in the mountedoperating state. Alternatively, a torsional barrier can also be ensuredby spot-welding the individual sheets 2.

The wings 31 on the inside like the outer wings 16 likewise serve forthe support, thermal compensation and/or centering of the oil guidingpipe 18. Furthermore, the three inner wings 31 form so-called “oil riserpockets”. In these pockets, the oil can flow back/rise coaxially alongthe oil guiding pipe 18 and flow into the respective level.

Cover 27 on the inside: the special feature here is that the outersurface should likewise be electropolished, for example. This reducesimpurities, which would be very harmful during evacuation, and reducesthe emittance of the surface and improves the outgassing rate. Areduction in the emittance leads to a reduction in the radiation losses.In addition, the polished surface has to be completely free of greaseand clean.

Base 19 on the inside: here, too, the outer surface should beelectropolished. This reduces impurities, which would be very harmfulduring evacuation, and reduces the emittance of the surface and improvesthe outgassing rate. A reduction in the emittance leads to a reductionin the radiation losses.

Furthermore, the inner base 19 should be designed in such a way that thelowermost PCM sheet 2 has a circumferential linear seating. Thisprevents a bypass leakage of the oil. In addition, the polished surfaceshould be completely free of grease and clean, which inter alia improvesthe outgassing rate. The geometry is advantageously such that the basehas a sufficient rigidity, in order to withstand the vacuum 9 and otherinfluences.

Casing, cover 6 and base 5 of the outer housing 3: the inner surface ofthe casing or housing 3 should likewise be electropolished, for example.This reduces impurities, which would be very harmful during evacuation,and reduces the emittance of the surface. A reduction in the emittanceleads to a reduction in the radiation losses. In addition, the polishedsurface should be completely free of grease and clean, which inter aliaimproves the outgassing rate. Beads in the casing on the outsidestabilize the casing under negative pressure inside. It is thereforepossible to use a thinner starting material.

The metal bellows 30 of the intake 10 and/or drain 11 has the task ofcompensating for the thermal expansion of the inner container 8. To thisend, about ten billows which can compensate for thermal stresses areintegrated in each bend. Furthermore, the metal bellows 30 should havethe smallest possible wall thickness together with the longest possibleoverall length. Heat losses as a result of heat conduction are thereforereduced.

The holders 23, 24 have the function of fixing the vacuum gap of theinner container 8 in relation to the outer container 3. In addition, theholders 23, 24 are preferably optimized in terms of their thermalconductivity, i.e. they are as long as possible with the smallestpossible cross section. Depending on the installed position of the store1, the holders 23, 24 are to be arranged in such a way that the legs 31of the holder 23, 24 are oriented parallel to the direction of greatestacceleration. In an application for vehicles, the axis of greatestacceleration is the Z axis of the vehicle (pitch holes). On account ofthe increased strength, the legs 31 of the holders 23, 24 are to beplaced under tensile load; this tensile loading is spring-loaded interalia by the spring 22 on the outside. The holders 23, 24 as well as all(metallic) elements which come into contact with the vacuum arepreferably to be treated appropriately, i.e. electropolished, clean,free of grease, etc.

The spring 22 on the outside should place the lower holder 24 undertensile preload in order to minimize oscillation of the inner container8.

Furthermore, the spring 22 is preferably in the form of a spiral spring,since spiral springs have the advantage of an extremely long wire lengthand thus have small heat losses as a result of thermal conductivity. Thematerial of the spring should be designed for common applications fortemperatures >about 350° C., since the spring preload has to be retainedafter the heat-treatment process for evacuation. The spring 22 as wellas all (metallic) elements which come into contact with the vacuum ispreferably to be treated appropriately, i.e. electropolished, clean,free of grease, etc.

Getter pellets 25: Getters “capture” free molecules which have not beenpumped out or have passed into the vacuum space 9 as a result ofmicroleakages and/or as a result of so-called “virtual leakages”, andbind them to the surface thereof. Following activation or regeneration(heating to >about 200° C.), the molecules bound to the surface diffuseinto the interior of the getter, where they are chemically bonded. Thesurface then has “free” points again in order to be able to bind foreignmolecules anew. Getters therefore make a large contribution tolengthening the life of the vacuum. Furthermore, they can shorten theevacuation time, since they likewise have a pump effect.

The getter holder 26 is to be designed preferably in such a way that itcan accommodate the getter pellets 25 in an advantageous manner. At thesame time, however, very little of the surface of the getter pellets 25should be concealed by the holder 26. Furthermore, the getter holder 26should conduct the externally applied activation temperature as well aspossible to and around the getter 25, such that the getter is activatedover the entire surface. The getter holder 26 as well as all (metallic)elements which come into contact with the vacuum is preferably to betreated appropriately, i.e. electropolished, clean, free of grease, etc.

The pinch pipe 7 or the connection 7 serves as a connection for a vacuumpump. The store is evacuated via the latter. The pinch pipe 7 ispreferably soldered or welded onto the cover 6. The pipe 7 is made ofcopper, for example, since copper can be deformed and pinched off in anadvantageous manner. Once the vacuum pressure has been reached, the pipe7 is pinched, for example by means of pliers or the like, cut off and atthe same time tightly welded. The pinch pipe 7 is to be designed to beas large as possible (e.g. >about 20 mm), since this represents thebottleneck upon evacuation.

LIST OF REFERENCE NUMERALS

-   1. Store-   2. Sheet-   3. Housing-   4. Casing-   5. Base-   6. Cover-   7. Connection-   8. Housing-   9. Vacuum-   10. Intake-   11. Drain-   12. Axis-   13. Stack-   14. Chamber-   15. Point-   16. Wing-   17. Comb-   18. Pipe-   19. Base-   20. End-   21. Spring-   22. Spring-   23. Spring-   24. Spring-   25. Pellet-   26. Holder-   27. Cover-   28. Sleeve-   29. Plate-   30. Bellows-   31. Wing-   32. Web-   33. Gap-   34. Inflow point-   35. Outflow point

1. Latent heat store comprising a plurality of heat exchanger units (2)which are arranged alongside one another and each comprise at least onephase change store (14), wherein the phase change stores (14) comprise astorage medium which has a phase change during operation and is intendedfor the storage of heat energy, wherein the heat exchanger units (2) arearranged within a heat exchanger housing (3, 8), wherein a heatexchanger fluid for heat exchange with the storage medium can flowthrough at least between adjacent heat exchanger units (2), wherein eachheat exchanger unit (2) has at least one associated inflow point toexpose the respective heat exchanger unit (2) to the flow of the heatexchanger fluid and an associated outflow point for the outflow of theheat exchanger fluid from the respective heat exchanger unit (2),characterized in that at least one common intake (10) for supplying theheat exchanger fluid to the heat exchanger units (2) and for dividingsaid fluid into a plurality of separate partial flow sections and alsoat least one common drain (11) for discharging the heat exchanger fluidfrom the heat exchanger units (2) and for bringing all partial flowsections together are provided, such that the heat exchanger units (2)arranged between the intake (10) and the drain (11) form a stack (13)collectively exposed to the flow, and such that the heat exchanger units(2) of the stack (13) collectively exposed to the flow are connected inparallel to one another, wherein the inflow point of the heat exchangerunit (2) is arranged in the central region of the heat exchanger unit(2) and the outflow point of the heat exchanger unit (2) is arranged inthe radially outwardly arranged casing region of the heat exchanger unit(2), or wherein the inflow point of the heat exchanger unit (2) isarranged in the radially outwardly arranged casing region of the heatexchanger unit (2) and the outflow point of the heat exchanger unit (2)is arranged in the central region of the heat exchanger unit (2), suchthat the heat exchanger fluid flows in the radial direction along theheat exchanger units (2) substantially over the entire cross sectionthereof, wherein the length of all partial flow sections of the heatexchanger fluid from the intake (10) to the drain (11) is substantiallyof equal length.
 2. Latent heat store according to the preamble of claim1 or according to claim 1, characterized in that at least one commonintake (10) for supplying the heat exchanger fluid to the heat exchangerunits (2) and for dividing said fluid into a plurality of separatepartial flow sections and also at least one common drain (11) fordischarging the heat exchanger fluid from the heat exchanger units (2)and for bringing all partial flow sections together are provided, suchthat the heat exchanger units (2) arranged between the intake (10) andthe drain (11) form a stack (13) collectively exposed to the flow, andsuch that the heat exchanger units (2) of the stack (13) collectivelyexposed to the flow are connected in parallel to one another, whereinthe inflow point of the heat exchanger unit (2) is arranged in thecentral region of the heat exchanger unit (2) and the outflow point ofthe heat exchanger unit (2) is arranged in the radially outwardlyarranged casing region of the heat exchanger unit (2), or wherein theinflow point of the heat exchanger unit (2) is arranged in the radiallyoutwardly arranged casing region of the heat exchanger unit (2) and theoutflow point of the heat exchanger unit (2) is arranged in the centralregion of the heat exchanger unit (2), such that the heat exchangerfluid flows in the radial direction along the heat exchanger units (2)substantially over the entire cross section thereof, wherein the flowresistances of all partial flow sections of the heat exchanger fluidfrom the intake (10) to the drain (11) are substantially of the samemagnitude.
 3. Latent heat store according to either of the precedingclaims, characterized in that all heat exchanger units (2) have asubstantially identical form.
 4. Latent heat store according to thepreamble of claim 1 or according to one of the preceding claims,characterized in that the heat exchanger units (2) have at least onespacer (16, 17, 31) for fixing a spacing for the heat exchanger fluid toflow through between the heat exchanger units (2).
 5. Latent heat storeaccording to one of the preceding claims, characterized in that thephase change stores (14) comprise at least the spacers (17).
 6. Latentheat store according to one of the preceding claims, characterized inthat the spacers (16, 31) are in the form of a bend (16, 31) of a heatexchanger unit (2).
 7. Latent heat store according to the preamble ofclaim 1 or according to one of the preceding claims, characterized inthat the heat exchanger units (2) have at least one anti-twist device(16, 15) for preventing twisting of heat exchanger units (2).
 8. Latentheat store according to one of the preceding claims, characterized inthat the spacers (16, 17, 31) of the heat exchanger units (2) are in theform of an anti-twist device (16).
 9. Latent heat store according to oneof the preceding claims, characterized in that the heat exchangerhousing (3, 8) has at least one thermal insulation unit (9) as asheathing.
 10. Latent heat store according to one of the precedingclaims, characterized in that the insulation unit (9) is in the form ofa vacuum insulation unit (9).
 11. Latent heat store according to one ofthe preceding claims, characterized in that the Vacuum insulation unit(9) at least in parts has a surface layer for reducing the emissionsinto the vacuum.
 12. Latent heat store according to one of the precedingclaims, characterized in that the vacuum insulation unit (8) comprisesat least one getter unit (25, 26) with a getter material.
 13. Latentheat store according to one of the preceding claims, characterized inthat at least one electric heating element for heating the phase changestores (14) and/or heat exchanger units (2) is arranged within the heatexchanger housing (3, 8).
 14. Latent heat store according to one of thepreceding claims, characterized in that the heating element is arrangedbetween two adjacent heat exchanger units (2).
 15. Latent heat storeaccording to one of the preceding claims, characterized in that theheating element is in the form of a heating foil.